Kinetic and equilibrium studies on the removal of 14C-ethion residues from wastewater by copper-based metal–organic framework
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There are compelling economic and environmental reasons to remove pesticides from wastewater because they are toxic and carcinogenic. The effectiveness of copper-based metal–organic framework (Cu-BTC) for adsorbing the insecticide 14C-ethion from wastewater has been studied as function of contact time, adsorbent dosage, temperature and pH. 14C-ethion/Cu-BTC isotherms exhibit two plateaus (BET type IV) and are reliably represented by Brunauer–Deming–Deming–Teller and Zhu–Gu models, with deviations of only 1.99 and 3.95%, respectively. The removal curve measured under batch operation is well represented by a pseudo-first-order equation, yielding results equivalent to the theoretical linear driving force model of Glueckauf. At pH 7, 75 mg L−1 ethion concentration, 150 min, 25 °C and 0.425 g L−1 Cu-BTC dose, the sorbent capacity is ca. 122 mg g−1. Moreover, Cu-BTC has a good stability after six adsorptions cycles. Finally, our results disclose the fundamental understanding of the adsorption mechanism: the ethion molecule coordinates to two copper(II) atoms across the metal–organic framework channel via the phosphoryl (P–O) group.
KeywordsAdsorption mechanism Copper-based metal–organic framework Ethion Kinetics Modeling Type IV isotherm
The authors would like to thank the help of Prof. Dr. H. Kamel, Radioisotopes Department, Atomic Energy Authority, Cairo, Egypt, in the radioactivity measurements. This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013) and UI QOPNA (Ref. FCT UID/QUI/00062/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.
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